Is there any resource out there that covers regular expression in a very basic starter level? I have looked at http://www.regular-expressions.info/ but it is not exactly 'quick reference' friendly.. any other sources?

When I was starting out with regular expressions I got recommended this book: Mastering Regular Expressions. It really helped me understand the basic concept and how regular expressions work. But also I can still learn from it today because it also covers more advanced topics.

There are some pdf versions of the books out there, but I don't think they are legal. Otherwise I would really recommend buying this book if you really like to actually understand regexp and not just copy ready regexps and kind of understand how it works.

+1000 Best book on regex ever. An excellent tutorial, it is clear, thorough, and even funny at times. The third edition covers PHP in-depth. The Slashdot review gave it 11 out of 10 and I wholeheartedly agree.
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ridgerunnerMay 7 '11 at 17:47

If you are on windows, you can use this program http://www.radsoftware.com.au/regexdesigner/
It's mostly for .net but can apply to any regex scenario.
There's a quick reference on the side and you can build and test your expressions.

Sams Teach Yourself Regular Expressions in 10 Minutes gave me a very good start. Everything about RegEx is not taught in 10 minutes but each different aspect of RegEx is broken in to easy to understand ~10 minute sessions.